This invention relates to curved rolls useful in the treatment of flexible webs and sheets. Such rolls have a bowed or curved axle which supports individual cylindrical tube sections or spools by way of roller bearings seated on the axle. The invention in particular provides such a roll having improved flexible couplings between the spools.
Curved rolls are employed in various industries for laterally expanding or contracting materials such as cloth, paper, plastic film, metal foil, tire cord webs and the like to remove wrinkles or to draw the sheet or web to a predetermined width. The rolls are also used for correcting the bow or curvature of weft elements in woven materials, and for controlling and guiding the path of webs and sheets in a processing plant.
When a curved roll is used without a resilient covering or sleeve over the spools; dirt, fibers, liquids, and other material external to the roll are to be sealed from the interior of the roll where they would degrade the bearings. Similarly, lubricant such as oil or grease within the roll for the bearings is to be sealed from leaking to the roll surface, where it would be lost from the bearings in addition to soiling the material running over the roll.
Further, the spools of such a roll are to be coupled torsionally to rotate together, but with flexibility to conform to the bow or curvature of the axle, the assemblage of spools is to rotate smoothly and without significant vibration or wobble at high speeds.
A prior effort to provide a roll structure which satisfies the foregoing objectives as set forth in United Kingdom Patent Specification No. 1,346,196 (which corresponds to German Pat. No. 1,635,360), couples each pair of adjacent spools with a flexible tubular coupling element having a metal bush in its interior bore. Each coupling element is telescopically seated within, and cemented or bonded to, the ends of the spools it interconnects. One shortcoming of this structure is a relatively high resistance of the roll to rotation, i.e. the roll has a relatively high torque requirement. This is due to a loss of energy in each coupling element as it is repeatedly deformed due to mechanical interactions with the skewed spools pressed against its outer surface and with the metal bush within it.
It is also known to couple the spools of a curved roll with a resilient elastic collar pressed within the spool ends and receiving at each end a series of drive pins fixed to the respective spools. However, this coupling structure tends to leak.
Accordingly, it is an object of this invention to provide an improved construction for a curved roll suitable for use without a sleeve or covering over the spools.
A further object of the invention is to provide a flexible torque coupling between the spools of a curved roll which seals material within the roll from leakage between the spools, and which seals the interior of the roll from external materials.
Another object of the invention is to provide a curved roll having a coupling of the above character and wherein the spools are in continuous positive torsional engagement with one another for smooth low-wear rotation at relatively high speeds. By way of example, rolls of the present type are subject typically to operation at high speeds in the order of 4,500 revolutions per minute.
It is also an object of the invention to provide a curved roll of the above character capable of sustained operation under adverse environmental conditions for relatively long periods of time. Attainment of this objective reduces maintenance and replacement of rolls. Adverse environmental conditions under which rolls typically operate, in addition to high rotational speeds, include exposure to corrosive fluids and to high temperatures. By way of example rolls at the wet end of a paper-making machine are exposed to the corrosive liquids present with ground wood paper stock, and rolls at the drier section are exposed to air or other drying gas at temperatures reaching as high as 300.degree. Fahrenheit. Other adverse conditions include the use of kerosine or like solvents for washing down paper-making equipment, and the presence of ozone under certain operating conditions.
The invention also has as an object to provide a roll having a relatively low resistance to rotation. Such a roll requires a relatively low rotational drive torque. In addition to yielding increased economy, this has the advantage of increasing the stretching or other treatment or control which the roll can impart to a web or sheet passing around it.
Other objects of the invention will in part be obvious and will in part appear hereinafter.